Why does Cascade exile?Late comment: I agree with @Affe, if only for the reason that there is a very similar mechanic in Ripple that uses revealed cards instead of exiled: Ripple 4 (When you cast this spell, you may reveal the top four cards of your library. You may cast any revealed cards with the same name as this spell without paying their mana costs. Put the rest on the bottom of your library.)

Resolving an ambiguous game state caused by mixing restricted mana@Rainbolt The comment makes perfect sense. There is no such thing as an "ambiguous game state caused by mixing restricted mana" if every player decision has been properly recorded. Every decision a player can legally make has a defined outcome. Just because players agree on mutually understood, even unspoken or implicit shortcuts does not mean the decisions have not been made.